A majority of the changes are not visible; these tweaks go along with recent updates that were made to Stack Overflow:

We updated the site's CSS to a newly refactored LESS system, so that it's easier for us to fix SE network CSS bugs globally and launch new features in the future.

We updated most of the graphics to SVG for retina support.

We have fixed a LOT of obscure bugs that arose when new features were not thoroughly tested across the entire network.

We've launching the shiny new user profile!

Visually it will "feel" the same as the old site with slight layout adjustments.

This update should retro-actively fix most of the old design bugs. Once the updates are live, I'll update this post. Then if you see any new bugs, or old ones not yet fixed, please post an answer here to let us know!

I found one other (minor) style issue, on the Select Your Next Badge screen:

The background of the container does not cover the entire contents of the dialog screen. I'm using Firefox 40.0.3 on Windows 2003, with no extensions enabled.

Update: My previous fix (now deleted) only masked the problem. The actual cause lies in the following rule (custom for Ask Patents, I think):

.subtabs a.youarehere, .filter a.youarehere {
font-weight: 700;
}

As you can see in the below image, the Search for a Badge.. box does not have enough room to display inline with the "Available", "All", "Gold", "Silver", "Bronze" links, because the font-weight: 700 makes the text wider, which forces the input field down to the next line and forces the all-badge-progress div out of the container.

Disabling this rule solves the problem:

This rule applies to several other aspects of the site and noticeably alters the visual appearance if it is disabled site-wide.

I requested a change to the default all.css in StackExchange Meta, to see if there is any agreement that this is a design issue with the new layout.